shared - i need it to be useful

[Atila Neves]

On Thursday, 18 October 2018 at 19:04:58 UTC, Erik van Velzen 
wrote:
> On Thursday, 18 October 2018 at 17:47:29 UTC, Stanislav Blinov 
> wrote:
>> On Thursday, 18 October 2018 at 17:17:37 UTC, Atila Neves 
>> wrote:
>>> On Monday, 15 October 2018 at 18:46:45 UTC, Manu wrote:
>>>> Assuming the rules above: "can't read or write to members", 
>>>> and the understanding that `shared` methods are expected to 
>>>> have threadsafe implementations (because that's the whole 
>>>> point), what are the risks from allowing T* -> shared(T)* 
>>>> conversion?
>>>
>>> int i;
>>> tid.send(&i);
>>> ++i;  // oops, data race
>>
>> Doesn't work. No matter what you show Manu or Simen here they 
>> think it's just a bad contrived example. You can't sway them 
>> by the fact that the compiler currently *prevents* this from 
>> happening.
>
> Manu said clearly that the receiving thread won't be able to 
> read or write the pointer.

Not directly - but obviously there must be *some* way to using 
it, in this case since it's an int with one of the core.atomic 
functions. At that point the spawned thread will be accessing it 
correctly, but the parent thread can modify the int in a 
non-atomic fashion.

> Because int or int* does not have threadsafe member functions.

https://dlang.org/phobos/core_atomic.html